● Option (3) is correct. High temperature about 94°C is required for the process of denaturation which is the first step of PCR. ● Ligation of DNA fragments is performed with the help of an enzyme called DNA ligase. ● Annealing is performed at 50°-60°C which is the second step that can get affected. ● Addition of nucleotides to the primer, synthesizing a new DNA strand using only the template sequences with the help of enzyme DNA polymerase is called primer extension/ polymerisation.